1. Field of the Invention
One or more embodiments of the present invention relate to a screen printing apparatus which prints paste such as cream solder or electrically conductive paste onto a board.
2. Description of Related Art
In an electronic component mounting step, screen printing is used as a method of printing paste such as cream solder, electrically conductive paste, etc., onto a board. In the method, a screen mask in which pattern holes are opened in accordance with print target positions is set on a board, paste is supplied onto the screen mask, and, when a squeegee is then slid, the paste is printed onto the board via the pattern holes. In the screen printing, the paste supplied onto the screen mask is scraped by the squeegee to be supplied to the whole printing width of the board. In the squeegeeing operation, the paste is scraped in the travel direction of the squeegee, and gradually pushed toward the outside along the surface of the squeegee. If the paste is moved to the outside range of the width dimension of the board, the paste in the outside range is not scraped by the squeegee and remains therein, since the screen mask in the outside range is not supported from the lower side and therefore easily warps. This may avoid normal squeegeeing operation.
In order to prevent the disadvantage from occurring, for example, JP-A-2013-123891 describes a screen printing apparatus which includes barrier members disposed on a squeegee at an interval corresponding to the printing width of a board, and which has a function of preventing paste on a screen mask from escaping to the outside of the printing width. In the screen printing apparatus, the barrier members are urged against the squeegee and the screen mask to restrict escape of the paste during the squeegeeing operation.